DEPOSITION PATTERNS OF INHALED RADON DECAY PRODUCTS IN HUMAN BRONCHIAL AIRWAY BIFURCATIONS

Particle deposition patterns within three-dimensional models of human bronchial airway bifurcations are simulated by a numerical fluid dynam ics and particle trajectory model. The three geometric models of a seg mental bronchial airway bifurcation, employed in the present study, ar e: 1) a symmetric ''idealized bifurcation model''; 2) a symmetric ''ph ysiologically realistic bifurcation model''; and, 3) an asymmetric ''i dealized bifurcation model''. Inspiratory deposition patterns for 1 nm (unattached radon progeny), 10 nm (ultrafine radon progeny), and 200 nm (attached radon progeny) particles reveal that particle deposition is enhanced at the carinal ridge, consistent with the action of local flow patterns. Carinal deposition enhancement is slightly higher for t he symmetric physiologically realistic and the asymmetric idealized mo dels relative to the commonly used symmetric idealized bifurcation mod el, thereby providing a reasonable range for local deposition enhancem ent factors. Together with reduced mucociliary clearance at carinal ri dges, such localized accumulations of radon decay products may produce local cellular doses, which can significantly exceed dose estimates b ased on uniform nuclide distributions. Copyright (C) 1996 Elsevier Sci ence Ltd.